Description:
<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Mild cognitive impairment (MCI) is an early stage of memory loss or cognitive decline and progresses to Alzheimer’s disease at a rate of about 15% per year. It is important to study the effects of MCI on the brain. Here we present a novel along‐tract analysis of microstructural brain metrics computed from diffusion MRI. We extract, map, and visualize the profile of microstructural abnormalities on 3D models of fiber tracts, yielding fine‐scale maps of the effects of MCI.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We analyzed multi‐shell diffusion‐weighted MRI data with 127 volumes from 131 ADNI3 participants (age: 55‐91years, 74F,57M). Participants included 44 with MCI and 87 cognitively normal controls (CN). Pre‐processed using the ADNI3 dMRI protocol. We applied multi‐shell‐multi‐tissue CSD and a probabilistic particle‐filtering‐tracking to generate whole‐brain tractograms. We applied DIPY’s BUAN tractometry pipeline to extract 30 white matter tracts from all subjects and evaluate the effects of MCI on 4 DTI measures (FA, MD, RD, and AD) along the length of the tracts. BUAN applies Linear‐Mixed‐Models with DTI measures set as the response variable, group mean modeled as fixed effects term, and subject‐specific mean as random effects term.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>We report significant group differences between MCI and CN in 6 bundles with <jats:italic>p</jats:italic>‐values<0.01 and <0.001 (Fig.1). In Fig.1 and Fig2, the columns and rows show results from six bundles for four DTI measures (see Fig.2 for keywords). Fig.2 highlights areas with significant differences on the tracts with black color where for MD, <jats:italic>p</jats:italic>‐values<0.001 and for the rest of the 3 measures, <jats:italic>p</jats:italic>‐values<0.01. Fig.3 reports significant effects of MCI on the rest of the tracts and measures with <jats:italic>p</jats:italic>‐values<0.001. We find lower mean FA and higher mean MD, AD, and RD in the MCI, compared to the control group.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>We applied the BUAN tractometry pipeline to map and visualize the effects of MCI on the white matter tracts of the brain. We found significant microstructural group differences in tracts where FA decreases and diffusivity measures increase in MCI participants.</jats:p></jats:sec>